/*
 * Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package java.net;

import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;

import sun.net.ConnectionResetException;

/**
 * This stream extends FileInputStream to implement a
 * SocketInputStream. Note that this class should <b>NOT</b> be
 * public.
 *
 * @author Jonathan Payne
 * @author Arthur van Hoff
 */
class SocketInputStream extends FileInputStream {

  static {
    init();
  }

  private boolean eof;
  private AbstractPlainSocketImpl impl = null;
  private byte temp[];
  private Socket socket = null;

  /**
   * Creates a new SocketInputStream. Can only be called
   * by a Socket. This method needs to hang on to the owner Socket so
   * that the fd will not be closed.
   *
   * @param impl the implemented socket input stream
   */
  SocketInputStream(AbstractPlainSocketImpl impl) throws IOException {
    super(impl.getFileDescriptor());
    this.impl = impl;
    socket = impl.getSocket();
  }

  /**
   * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
   * object associated with this file input stream.</p>
   *
   * The {@code getChannel} method of {@code SocketInputStream}
   * returns {@code null} since it is a socket based stream.</p>
   *
   * @return the file channel associated with this file input stream
   * @spec JSR-51
   * @since 1.4
   */
  public final FileChannel getChannel() {
    return null;
  }

  /**
   * Reads into an array of bytes at the specified offset using
   * the received socket primitive.
   *
   * @param fd the FileDescriptor
   * @param b the buffer into which the data is read
   * @param off the start offset of the data
   * @param len the maximum number of bytes read
   * @param timeout the read timeout in ms
   * @return the actual number of bytes read, -1 is returned when the end of the stream is reached.
   * @throws IOException If an I/O error has occurred.
   */
  private native int socketRead0(FileDescriptor fd,
      byte b[], int off, int len,
      int timeout)
      throws IOException;

  // wrap native call to allow instrumentation

  /**
   * Reads into an array of bytes at the specified offset using
   * the received socket primitive.
   *
   * @param fd the FileDescriptor
   * @param b the buffer into which the data is read
   * @param off the start offset of the data
   * @param len the maximum number of bytes read
   * @param timeout the read timeout in ms
   * @return the actual number of bytes read, -1 is returned when the end of the stream is reached.
   * @throws IOException If an I/O error has occurred.
   */
  private int socketRead(FileDescriptor fd,
      byte b[], int off, int len,
      int timeout)
      throws IOException {
    return socketRead0(fd, b, off, len, timeout);
  }

  /**
   * Reads into a byte array data from the socket.
   *
   * @param b the buffer into which the data is read
   * @return the actual number of bytes read, -1 is returned when the end of the stream is reached.
   * @throws IOException If an I/O error has occurred.
   */
  public int read(byte b[]) throws IOException {
    return read(b, 0, b.length);
  }

  /**
   * Reads into a byte array <i>b</i> at offset <i>off</i>,
   * <i>length</i> bytes of data.
   *
   * @param b the buffer into which the data is read
   * @param off the start offset of the data
   * @param length the maximum number of bytes read
   * @return the actual number of bytes read, -1 is returned when the end of the stream is reached.
   * @throws IOException If an I/O error has occurred.
   */
  public int read(byte b[], int off, int length) throws IOException {
    return read(b, off, length, impl.getTimeout());
  }

  int read(byte b[], int off, int length, int timeout) throws IOException {
    int n;

    // EOF already encountered
    if (eof) {
      return -1;
    }

    // connection reset
    if (impl.isConnectionReset()) {
      throw new SocketException("Connection reset");
    }

    // bounds check
    if (length <= 0 || off < 0 || off + length > b.length) {
      if (length == 0) {
        return 0;
      }
      throw new ArrayIndexOutOfBoundsException();
    }

    boolean gotReset = false;

    // acquire file descriptor and do the read
    FileDescriptor fd = impl.acquireFD();
    try {
      n = socketRead(fd, b, off, length, timeout);
      if (n > 0) {
        return n;
      }
    } catch (ConnectionResetException rstExc) {
      gotReset = true;
    } finally {
      impl.releaseFD();
    }

        /*
         * We receive a "connection reset" but there may be bytes still
         * buffered on the socket
         */
    if (gotReset) {
      impl.setConnectionResetPending();
      impl.acquireFD();
      try {
        n = socketRead(fd, b, off, length, timeout);
        if (n > 0) {
          return n;
        }
      } catch (ConnectionResetException rstExc) {
      } finally {
        impl.releaseFD();
      }
    }

        /*
         * If we get here we are at EOF, the socket has been closed,
         * or the connection has been reset.
         */
    if (impl.isClosedOrPending()) {
      throw new SocketException("Socket closed");
    }
    if (impl.isConnectionResetPending()) {
      impl.setConnectionReset();
    }
    if (impl.isConnectionReset()) {
      throw new SocketException("Connection reset");
    }
    eof = true;
    return -1;
  }

  /**
   * Reads a single byte from the socket.
   */
  public int read() throws IOException {
    if (eof) {
      return -1;
    }
    temp = new byte[1];
    int n = read(temp, 0, 1);
    if (n <= 0) {
      return -1;
    }
    return temp[0] & 0xff;
  }

  /**
   * Skips n bytes of input.
   *
   * @param numbytes the number of bytes to skip
   * @return the actual number of bytes skipped.
   * @throws IOException If an I/O error has occurred.
   */
  public long skip(long numbytes) throws IOException {
    if (numbytes <= 0) {
      return 0;
    }
    long n = numbytes;
    int buflen = (int) Math.min(1024, n);
    byte data[] = new byte[buflen];
    while (n > 0) {
      int r = read(data, 0, (int) Math.min((long) buflen, n));
      if (r < 0) {
        break;
      }
      n -= r;
    }
    return numbytes - n;
  }

  /**
   * Returns the number of bytes that can be read without blocking.
   *
   * @return the number of immediately available bytes
   */
  public int available() throws IOException {
    return impl.available();
  }

  /**
   * Closes the stream.
   */
  private boolean closing = false;

  public void close() throws IOException {
    // Prevent recursion. See BugId 4484411
    if (closing) {
      return;
    }
    closing = true;
    if (socket != null) {
      if (!socket.isClosed()) {
        socket.close();
      }
    } else {
      impl.close();
    }
    closing = false;
  }

  void setEOF(boolean eof) {
    this.eof = eof;
  }

  /**
   * Overrides finalize, the fd is closed by the Socket.
   */
  protected void finalize() {
  }

  /**
   * Perform class load-time initializations.
   */
  private native static void init();
}
